tailieunhanh - Characterization of commercial natural rubber purified with transesterification

The resulting TE-NRs were characterized by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and size exclusion chromatography (SEC). Epoxy group was found for PC, STR5L, RSS3, TSS8® and SMR20 and trans-1,4-isoprene unit from trans-1,4-isoprene units from cis-trans isomerization was found for TSS8® and SMR20 from the assignments of 1H-NMR signals. | Vietnam Journal of Chemistry, International Edition, 54(4): 483-487, 2016 DOI: Characterization of commercial natural rubber purified with transesterification Nghiem Thi Thuong1*, Phan Trung Nghia1, Seiichi Kawahara2 1 Department of Physical Chemistry, School of Chemical Engineering, Hanoi Univeristy of Science and Technology, Hanoi, Vietnam 2 Department of Materials Science and Technology, Faculty of Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan Received 26 May 2016; Accepted for publication 12 August 2016 Abstract Highly purified commercial natural rubbers were prepared and characterized to elucidate the effect of processing condition on structure characteristic of the rubbers. In the present study, various commercial rubbers, . Pale Crepe (PC), Ribbed Smoked Sheet (RSS3), Technically Specified Sheet (TSS8®), Standard Thailand Rubber (STR5L) and Standard Malaysian Rubber (SMR20) were purified by acetone extraction and transesterification (TE) to prepare highly purified commercial rubbers (TE-NR). The resulting TE-NRs were characterized by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and size exclusion chromatography (SEC). Epoxy group was found for PC, STR5L, RSS3, TSS8® and SMR20 and trans-1,4-isoprene unit from trans-1,4-isoprene units from cis-trans isomerization was found for TSS8® and SMR20 from the assignments of 1H-NMR signals. This result implies that the degradation, that is epoxidation and isomerization, took place during the processing of commercial rubbers. The damage of commercial natural rubbers was investigated with respect to its molecular weight. Keywords. Commercial rubber, transesterification, NMR, epoxidation, isomerization. 1. INTRODUCTION Natural rubber (NR) obtained from Hevea brasiliensis is widely known to be a strategic material which exhibits outstanding mechanical properties such as high resilience, a low heat .